Abstract: A server according to an embodiment includes a processor configured to receive a friend add request for a target account from a user terminal accessed with a user account; based on one of the user account and the target account being a protected account, transmit an approval request for the friend add request to a protector account connected to the protected account; and based on receiving a reply to the approval request from the protector terminal, add the target account to a friend list of the user account.

Abstract: According to the present invention, a deuterium-substituted marker for fuel is synthesized through substitution with deuterium so as to have structurally and chemically similar properties to those of a molecule configuring fuel oil. A molecule of the deuterium-substituted marker is significantly similar to the conventional molecule configuring the fuel oil, which may prevent illegal removal of the marker by the fake oil manufacturers. According to the present invention, it is able to pursue public safety and environmental protection from fake oil products, and to prevent national tax evasion, by preventing the illegal mixing of fuel oil to secure a legal distribution of the oil market according to the present invention.

Abstract: Provided are non-exposure supplied fuel quantity testing device and method of a vehicle-mounted type, and more particularly, a device formed in a trunk of a vehicle without being exposed to test whether or not the ordered fuel quantity is supplied at the time of supplying fuel. Since the device is formed so as not to be exposed, it is disable to perform an artificial tampering of a lubricator, and since the device is mounted in the trunk, it is enable to measure whether or not the ordered fuel is supplied accurately at the same time as supplying fuel. The present invention relates to a testing method using the testing device.

Abstract: According to the present invention, a deuterium-substituted marker for fuel is synthesized through substitution with deuterium so as to have structurally and chemically similar properties to those of a molecule configuring fuel oil. A molecule of the deuterium-substituted marker is significantly similar to the conventional molecule configuring the fuel oil, which may prevent illegal removal of the marker by the fake oil manufacturers. According to the present invention, it is able to pursue public safety and environmental protection from fake oil products, and to prevent national tax evasion, by preventing the illegal mixing of fuel oil to secure a legal distribution of the oil market according to the present invention.

Abstract: Provided are non-exposure supplied fuel quantity testing device and method of a vehicle-mounted type, and more particularly, a device formed in a trunk of a vehicle without being exposed to test whether or not the ordered fuel quantity is supplied at the time of supplying fuel. Since the device is formed so as not to be exposed, it is disable to perform an artificial tampering of a lubricator, and since the device is mounted in the trunk, it is enable to measure whether or not the ordered fuel is supplied accurately at the same time as supplying fuel. The present invention relates to a testing method using the testing device.